using System;

using System.Numerics;

public class Program

{

    public static void Main()

    {

​

        string[] firstLine = Console.ReadLine().Split(' ');

        int nailNo = int.Parse(firstLine[0]);

        int radius = int.Parse(firstLine[1]);

​

        Vector2[] points = new Vector2[nailNo];

​

        for (int i = 0; i < nailNo; i++)

        {

            string[] line = Console.ReadLine().Split(' ');

            points[i] = new Vector2(float.Parse(line[0]), float.Parse(line[1]));

        }

​

        float ropeLenght = 0;

​

        for (int i = 0; i < points.Length; i++)

        {

            ropeLenght += Vector2.Distance(points[i], points[(i < points.Length -1) ? i+1 : 0]);

        }

​

        ropeLenght += 2 * (float)Math.PI * radius;

        Console.WriteLine("Length is: " + ropeLenght.ToString("#0.00"));

    }

}